The present disclosure relates to energy management, and more particularly to power consuming device control methods and electrical energy consumption systems. This disclosure finds particular application to controlling when power consuming devices are started after a demand response event.
Many utilities are currently experiencing a shortage of electric generating capacity due to increasing consumer demand for electricity. Currently utilities generally charge a flat rate, but with increasing cost of fuel prices and high energy usage at certain parts of the day, utilities have to buy more energy to supply customers during peak demand. Consequently, utilities are charging higher rates during peak demand. If peak demand can be lowered, then a potential huge cost savings can be achieved and the peak load that the utility has to accommodate is lessened. In order to reduce high peak power demand, many utilities have instituted time of use metering and rates which include higher rates for energy usage during on-peak times and lower rates for energy usage during off-peak times. As a result, consumers are provided with an incentive to use electricity at off-peak times rather than on-peak times.
One outcome of utilities varying the price of electrical energy over time is a reduction in consumption during the on-peak times and a greater consumption during the off-peak times. Presently, to take advantage of the lower cost of electricity during off-peak times, a controller can switch the actual energy supply to the power consuming device on and off and/or switch the operating mode of the power consuming device between a normal operating mode and a resource savings mode. For example, during off-peak times the controller can decrease the setpoint temperature of an HVAC system and during on-peak times the controller can increase the setpoint temperature and/or turn the system off.
While the initiation of operation of power consuming devices immediately after a change in rate, for example, do not appear to affect the individual consumer, the operation of many power consuming devices in this manner can create a tremendous load on the power distribution network. For example, some power consuming devices, such as HVAC systems, require six times their normal operating currents during start up. When a number of those power consuming devices switch from a resource savings mode back to a normal operating mode, the influx of current may be up to six times the normal load on the power grid. This initial influx can compromise the integrity of the power grid and, at when the power grid is fully loaded, result in a reduction or shut off in the power supplied to consumers. These reductions and shut-offs of power are commonly known as brown-outs or black-outs. Therefore, there is a need to provide an improved system that can control when power consuming devices are started after a demand response event.